This invention relates to lasers and more particularly, to a solid state laser whose laser medium is a strontium aluminum fluoride crystal doped with chromium, SrAlF.sub.5 :Cr.sup.3+. A number of solids have been found to be suitable for laser action. Generally, the laser active materials involve a rare earth, actinide, or transition metal dopant in a crystalline or glass host. Laser action has been demonstrated in alexandrite (BeAl.sub.2 O.sub.4 :Cr.sup.3+), a naturally occurring mineral having the chrysoberyl structure. Laser action has also been demonstrated in a single crystal of emerald (Be.sub.3 Al.sub.2 (SiO.sub.3).sub.6 :Cr.sup.3+). Both alexandrite and emerald lasers have a tuning range centered around 750 nm.
It is very desirable to have a solid state laser medium having a tuning range centered around 850 nm, that is, a shift of 100 nm toward the infrared as compared to an emerald or alexandrite lasing medium. A solid state laser having a wavelength tuning range centered around 850 nm will be extremely useful as a tunable source in spectroscopic scientific research. Such a solid state laser would be a replacement for liquid dye lasers which are unstable, hard to work with and messy. In addition, because second harmonic generation of 850 nm is in the blue portion of the spectrum, a laser operable in this region would be useful for communicating through water since light in this portion of the spectrum propagates efficiently through water. It is also desirable to have a solid state laser medium which not only has a wavelength tuning range centered around 850 nm, but also has a laser gain of 2-3 times higher than for emerald or alexandrite at room temperature.
It is therefore an object of this invention to provide a solid state laser including a laser medium whose tuning range is centered around 850 nm.
A further object of the invention is a solid state laser medium having a laser gain 2-3 times higher than that for alexandrite and emerald.
Yet another object of the invention is such a laser medium which is substantially temperature insensitive at room temperature.